The present invention relates in general to a method and apparatus for supplying power to an automotive multimedia/personal computer system, and, more specifically, to a power management strategy which reduces vehicle battery consumption while reducing typical boot-up time of an automotive multimedia computer-based system.
Power management is an important issue in portable computing devices. This is especially true in mobile vehicles which have a limited battery capacity and which have stringent current limitations. As microprocessor-based systems become more powerful by using larger microprocessors and using a greater number of peripheral devices, power requirements increase. In vehicles containing an internal combustion engine and alternator, electric power generation may be sufficient to operate without much difficulty. In vehicles using other power plants or in an internal combustion engine vehicle with the engine shut off, significant limitations may be placed on current consumption (both normal operating current and quiescent current) of the multimedia/PC system.
Partly due to available power limitations, microprocessors having low power requirements are normally used in mobile vehicles. As mobile computing functions have been introduced into vehicles, reduced instruction set computing (RISC) microprocessors have been chosen since they are smaller and consume less power. Thus, complex instruction set computing (CISC) microprocessors such as Intel Pentium (xc3x9786) microprocessors and the Motorola 680xc3x970 family of microprocessors have been avoided. However, RISC microprocessors often cannot run the same software as has been created for CISC microprocessors. Availability of operating system and applications software is much greater for CISC microprocessors because of the popularity of desktop and laptop personal computers. Therefore, it would be very beneficial to use a CISC microprocessor in a mobile vehicle.
An important performance issue for a multimedia/personal computer based system in a mobile vehicle is boot-up time. A multimedia system may be providing information, communication, entertainment, or other functions which the vehicle user may expect to be available as soon as the vehicle ignition switch is turned on. By example, the multimedia system may include a navigation function and the driver may want to initiate input of a desired destination as soon as possible after turning on the vehicle. By maintaining full or partial power to the multimedia system, boot-up time can be reduced or eliminated, but this conflicts with the need to minimize power consumption. CISC microprocessors such as the Pentium typically have reduced power states in which processing operations are suspended while the state of the memory and the internal microprocessor state are stored. Such a reduced power state may be entered in response to various conditions monitored by the microprocessor. However, the microprocessor can""t go completely to sleep and still monitor the conditions which should wake it up. Furthermore, if the microprocessor has sole responsibility to conduct its own power management, then there is limited ability to recover from errors.
The present invention has the advantages of providing efficient and robust power management of an in-vehicle multimedia/personal computer-based system, allowing a CISC processor to operate in a mobile environment with low power consumption and fast boot-up time.
The present invention provides a loosely coupled power management strategy in which the majority of power management functions are performed by a low power microprocessor separate from the CISC computing device.
In one aspect of the invention, a vehicle information, communication and entertainment system provides mobile operation of information, communication and entertainment devices in a vehicle. The vehicle has a vehicle powered state and a vehicle unpowered state. A main motherboard contains a main application microprocessor, random access memory, and a power management chip set that controls power to the main application microprocessor and the memory. A power controller and regulator supplies a plurality of regulated voltages to the power management chip set and to at least one device remotely located from the main motherboard. A user control places the information, communication and entertainment system into an active user state or an inactive user state. A reduced power microprocessor controls the switching on and off of the regulated voltages in response to the user control and whether the vehicle is in the vehicle powered state or the vehicle unpowered state.